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- Thread starter gina4930
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- #2

Dick

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You can't just ask a question here. You need to show an attempt. Label some variables and try it.

- #3

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x=8ft

cos(theta)=x/10

-sin(theta)*dtheta/dt=1/10 * dx/dt

-sin(.644) * dtheta/dt=1/10 * 1.1

dtheta/dt=-.183

I'm not getting the correct answer. I don't know what I'm doing wrong. Help!

- #4

Mark44

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x=8ft

cos(theta)=x/10

-sin(theta)*dtheta/dt=1/10 * dx/dt

-sin(.644) * dtheta/dt=1/10 * 1.1

dtheta/dt=-.183

I'm not getting the correct answer. I don't know what I'm doing wrong. Help!

Did you draw a picture of the situation?

What does x represent? You have that x = 8ft. Does this mean that x is always 8 ft or just at a particular moment?

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- #5

Dick

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x=8ft

cos(theta)=x/10

-sin(theta)*dtheta/dt=1/10 * dx/dt

-sin(.644) * dtheta/dt=1/10 * 1.1

dtheta/dt=-.183

I'm not getting the correct answer. I don't know what I'm doing wrong. Help!

That actually looks pretty good unless I am missing something too. There is an easier and more accurate way to find sin(theta) than the way you did it, though. Do you know what the answer you are supposed to get is?

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Dick- What is the more accurate way to find sin(theta)? I don't know what the correct answer is supposed to be. It's an online problem so I would assume it needs to be as specific as possible. My previous answers include: -.183 , -.2 , and -.1375 all in rad/s. Would it be possible for the answer to be positive?

- #7

Dick

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Dick- What is the more accurate way to find sin(theta)? I don't know what the correct answer is supposed to be. It's an online problem so I would assume it needs to be as specific as possible. My previous answers include: -.183 , -.2 , and -.1375 all in rad/s. Would it be possible for the answer to be positive?

You found theta by using cos(theta)=8/10 since the adjacent side is 8 and the hypotenuse is 10. What's the opposite side? Use it to find sin(theta) directly.

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- #9

Dick

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I would say your answer SHOULD be correct. My only other suggestion is that you can write sin(theta)=6/10 exactly. Do you see why?

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- #11

Mark44

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Maybe they're looking for an answer in degrees/sec.

- #12

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So you should first get a function of θ(t), then derive and then replace time t with the time that the ladder would be 8 feet from the ground.

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